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OBSERVATIONS  O> 


AGRICL  ,-* 

•      LIBRARY 

OBSERVATIONS  ON  RHIZINA  INFLATA 

By  JAMES  R.  WEIR, 

Forest  Pathologist,  Investigations  in  Forest  Pathology, 
Bureau  of  Plant  Industry 

Considerable  doubt  exists  regarding  the  parasitism  of  Rhizina  inflata 
(Schaff.)  Sacc.  (R.  undulata  Fr.).  This  peculiar  fungus  (PL  VIII,  figs. 
1,2,  and  3)  occurs  quite  abundantly  on  the  ground  in  the  forest-fire  areas 
of  the  Northwest.  Usually  found  as  a  saprophyte  on  the  burned  forest 
soil,  it  attracted  little  attention  until  the  close  proximity  of  the  fruiting 
bodies  to  dead  coniferous  seedlings  was  noted  to  be  of  frequent  occur- 
rence. A  close  examination  of  the  roots  of  the  dead  seedlings  showed 
the  mass  of  white  mycelium  clinging  to  and  ramifying  in  the  cortical 
tissues  of  the  root  to  be  in  connection  with  the  near-by  fruiting  structures 
of  Rhizina  inflata.  In  some  cases  the  sporophores  of  this  fungus  sur- 
rounded the  stem  of  the  seedling. 

The  observations  on  the  parasitism  of  this  fungus  are  not  extensive. 
The  disease  "la  maladie  du  rond"  of  Pinus  sylvestris  and  P.  maritima, 
according  to  the  investigations  of  Prillieux  and  De  la  Boulaye  (iSSo),1 
is  accredited  to  this  fungus.  Hartig  (1891,  1892,  1894,  p.  123-129) 
afterwards  in  more  thorough  investigations  substantiated  the  observa- 
tions of  the  former  investigators  and  showed  Rhizina  inflata  to  be  capable 
of  living  as  a  true  parasite,  causing  the  death  of  4- year-old  seedlings  of 
Abies  pectinata,  Pinus  strobus,  Larioc  europaea,  Picea  sitkaensis,  Tsuga 
mertensiana,  Pseudotsuga  douglasii,  and  Castanea  vesca.  Von  Tubeuf  ( 1 897 , 
p.  273)  also  reports  the  fungus  as  a  parasite  in  the  forest-tree  nurseries 
of  Germany  and  in  the  natural  forests  of  Pinus  pinaster  in  France. 

Early  in  the  spring  of  1912  at  a  certain  point  along  an  old  logging  road 
in  the  Kaniksu  National  Forest,  Idaho,  where  the  brush  had  been  burned, 
young  3-  to  5-year-old  seedlings  of  Tsuga  heterophylla,  Larioc  occidentalis, 
and  Pinus  monticola  were  observed  to  be  dying  in  small  isolated  patches. 
The  roots  of  the  seedlings  on  being  pulled  up  were  closely  matted  together 
by  a  white  mycelium,  causing  a  quantity  of  earth  to  adhere  to  them. 
Since  fungous  fruiting  bodies  were  not  in  evidence  on  any  part  of  the 
diseased  plants  or  on  the  ground  around,  the  death  of  the  seedlings  was 
attributed  to  Armillaria  mellea  (Vahl)  Quel.,  which  is  very  abundant  in 
this  region  and  is  frequently  the  cause  of  the  death  of  very  young  growth. 
The  mycelium  had  penetrated  all  parts  of  the  cortical  and  bast  tissues  of 
che  roots,  causing  them  to  become  saturated  with  resin,  a  condition 
quite  similar  to  that  produced  by  A.  mellea.  The  diseased  areas  were 

1  Citations  to  literature  in  parentheses  refer  to  "  Literature  cited,"  p.  95. 

Journal  of  Agricultural  Research,  Vol.  IV,  No.  i 

Dept.  of  Agriculture,  Washington,  D.  C.  Apr.  15, 1915 

G-44 
(93) 


94  Journal  of  Agricultural  Research  VOI.IV.NO.  i 

from  2  to  4  feet  in  diameter  and  were  irregularly  circular  in  shape,  as  if 
the  causal  agent  had  started  from  the  center. 

Later  in  the  season,  near  the  borders  of  these  areas  and  at  the  base  of 
the  stems  of  the  dead  seedlings,  deep-brown,  effused,  undulating,  fruit- 
ing structures  appeared,  which  were  at  once  recognized  as  those  of  Rhizina 
inflata  (PI.  VIII,  fig.  2).  As  to  the  connection  of  these  fruiting  struc- 
tures with  the  mycelium  beneath  them  in  the  forest  mold  and  with  that  of 
the  roots  of  the  diseased  seedlings,  there  seemed  little  room  for  doubt.  It 
did  not  seem  probable  that  the  base  of  the  diseased  plant  would  be  com- 
pletely inclosed  by  the  fruiting  structure,  with  its  peculiar  rootlike  fibrils 
(PI.  VIII,  fig.  3)  mingling  with  the  mass  of  mycelium  about  the  diseased 
roots,  without  having  some  connection  with  it.  Such  a  seedling  with  fruit- 
ing body  attached  was  carefully  removed  from  the  soil  and  placed  in  a  dish 
of  water,  in  order  to  allow  the  attached  earth  to  fall  gradually  away. 
It  was  found  that  the  numerous  rhizoids  or  strands  of  mycelium  by  which 
the  fruiting  structures  are  attached  to  the  substratum  were  continuous 
with  the  mycelium  surrounding  the  diseased  roots.  These  roots  were 
microscopically  examined  and  showed  that  the  internal  mycelial  system 
ramifying  in  the  cortical  parenchyma  and  in  the  sieve  tubes  of  the  bast 
was  a  continuation  of  the  mycelium  which  connected  up  the  rhizoid 
strands  of  the  fruit  body. 

By  shaking  in  boiled  water  a  quantity  of  soil  which  had  been  burned 
over  the  previous  year  and  which  showed  no  signs  of  fungous  growth,  a 
solution  was  prepared  to  which  a  large  quantity  of  spores  of  Rhizina 
inflata  was  added.  This  solution  was  thoroughly  sprayed  about  the  base 
of  several  healthy  3-  to  4- year-old  white-pine  seedlings  (Pinus  monticola) 
growing  on  burned  ground  in  another  part  of  the  forest.  The  sprayed 
seedlings  appeared  slightly  reduced  in  vigor  in  the  fall  of  1912  and  by 
July  of  1913  they  were  dead.  The  roots  of  each  were  infected  by  the 
same  clinging  mass  of  mycelium  previously  described.  The  stems  and 
leaves  were  free  from  any  other  diseases.  It  is  believed  that  this  result, 
although  not  obtained  under  control  conditions,  furnishes  some  experi- 
mental proof  of  the  parasitism  of  Rhizina  inflata  as  it  occurs  in  the 
Northwest. 

Underwood  (1896)  reports  the  distribution  of  the  species  as  follows: 
Connecticut  (Thaxter),  New  York  (Peck),  Rhode  Island  (Bennett),  Penn- 
sylvania (Schweinitz),  Wisconsin  (Bundy),  North  Carolina  and  South 
Carolina  (Curtis).  The  range  of  Rhizina  inflata  is  further  extended  by 
the  writer,  who  has  collected  it  at  the  following  stations:  Priest  River, 
Idaho,  in  Kaniksu  National  Forest  on  Pinus  monticola,  Tsuga  heterophylla, 
and  l^arix  occidcntalis;  Coeur  d'Alene  National  Forest,  Idaho,  on  Pinus 
monticola  and  Abies  grandis;  Thompson  Falls,  Mont.,  in  Cabinet  National 
Forest,  on  Pinus  contorta;  Missoula  National  Forest,  Mont.,  on  Pinus 
ponderosa;  Lolo  National  Forest,  Mont.,  on  Pinus  monticola;  Ely,  Minn., 
in  Superior  National  Forest,  on  Pinus  divaricata;  and  Salmon  Arm, 
British  Columbia,  on  Pseudotsuga  taxijolia. 


Apr.  15, 1915  Observations  on  Rhizina  Inflata  95 

LITERATURE:  CITED 

HARTIG,  Robert. 

1891.  Untersuchungen  iiber  Rhizina  undulata.     In  Bot.  Centbl.,  Bd.  45,  No.  18, 

p.  237-238. 

1892.  Rhizina  undulata  Fr.     Der  Wurzelschwamm.     In  Forstl.  Naturw.  Ztschr., 

Jahrg.  i,  Heft  8,  p.  291-297,  10  fig. 
1894.  Text- Book  of  the  Diseases  of  Trees.     Trans,  by  William  Somerville,  rev. 

and  ed.  by  H.  M.  Ward.     331  p.,  159  fig.     London  and  New  York. 
PRILUEUX,  E.  E-,  AND  BOULAYE,  Seurrat  de  la. 

1880.  [Quelques  renseignements  sur  la  maladie  dite  du  rond  dans  les  pineraies.] 

In  Compt.  Rend.  Soc.  Agr.  France,  t.  u,  p.  386-389. 
TUBEUF,  Karl  von. 

1897.  Diseases  of  Plants  Induced  by  Cryptogamic  Parasites     .     .     .     Eng.  ed. 

by  W.  G.  Smith.     598  p.,  330  fig.     London,  New  York,  and  Bombay. 
UNDERWOOD,  L.  M. 

1896.  On  the  distribution  of  the  North  American  Helvellales.     In  Minn.  Bot. 
Studies,  v.  i,  p.  483-500. 


PLATE  VIII 

Fig.  i. — Mature  fruiting  structure  of  Rhizina  inflata,  showing  the  undulating  upper 
surface. 

Fig.  2. — Immature  fruiting  structure  of  Rhizina  inflata. 

Fig.  3. — Fruiting  structure  of  Rhizina  inflata,  showing  the  peculiar  mycelial  strands 
or  fibrils  by  which  the  fruiting  body  is  attached  to  the  substratum. 

(96) 


Rhizina  Inflata 


PLATE  VIII 


Journal  of  Agricultural  Research 


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